The present invention relates to a method of programming a non-volatile memory device. More particularly, the invention relates to a method of programming a non-volatile memory device which requires less time for programming and is capable of reducing coupling effect due to a programming sequence and/or cell distribution.
Non-volatile memory devices are electrically programmable and erasable and are able to retain stored data when supplied power is interrupted. Flash memory is one type of non-volatile memory and uses an electrical charge to store data. Each of the memory cells forming a flash memory device includes a control gate, a charge storage layer, and a cell transistor having a source and a drain. The flash memory device changes the data value stored by a memory cell by controlling the quantity of charge accumulated on the charge storage layer of the memory cell.
The cell transistor of the flash memory device controls the quantity of charge stored on the charge storage layer using the so-called F-N tunneling phenomenon. An erase operation may be performed in relation to a cell transistor by applying a ground voltage to the control gate and by applying a voltage higher than a constituent power supply voltage to the semiconductor substrate (or bulk). Under these erase bias conditions, a strong electric field is formed between the charge storage layer and the semiconductor bulk due to a large difference in the electrical resistances of same. As a result, charge accumulated on the charge storage layer is discharged by F-N tunneling, and the critical voltage of the erased cell transistor decreases.
A programming operation may be performed in relation to the cell transistor by applying a voltage higher than the power supply voltage to the control gate and applying a ground voltage to the drain, as well as the semiconductor bulk. Under these programming bias conditions, charge accumulates on the charge storage layer due to F-N tunneling, and the critical voltage of the cell transistor increases.
Hence, a memory cell state in which charge is relatively absent from the charge storage layer and the corresponding critical voltage of the cell transistor is negative is conventionally referred to as an erased state. Further, a memory cell state in which charge accumulates on the charge storage layer and the corresponding critical voltage of the cell transistor is greater than zero is referred to as a programmed state.